Method for Forming Anti-Reflective Coating

ABSTRACT

A method of forming an antireflective coating on an electronic device comprising (A) applying to an electronic device an ARC composition comprising (i) a silsesquioxane resin having the formula (PhSiO (3-X)/2 (OH) x)m HSiO (3-x)/2 (OH) x)N (MeSiO (3-x)/2 (OH) x)p  where Ph is a phenyl group, Me is a methyl group, x has a value of 0, 1 or 2; m has a value of 0.05 to 0.95, n has a value of 0.05 to 0.95, p has a value of 0.05 to 0.95, and m+n+p≈1; and (ii) a solvent; and (B) removing the solvent and curing the silsesquioxane resin to form an antireflective coating on the electronic device.

With the continuing demand for smaller feature sizes in thesemiconductor industry, 193 nm optical lithography has emerged veryrecently as the technology to produce devices with sub-100 nm. The useof such shorter wavelength of light requires the bottom antireflectivecoating (BARC) to reduce the reflection on the substrate and dampen thephotoresist swing cure by absorbing light that has been passed throughthe photoresist. Commercially available antireflective coatings (ARC)consist of both organic and inorganic materials. Typically, theinorganic ARC, which exhibit good etch resistant, is CVD based and issubject to all of the integration disadvantage of extreme topography.The organic ARC materials are applied by spin-on process and haveexcellent fill and planarization properties, but suffer from poor etchselectivity to organic photoresist. As a result, a material that offersthe combined advantages of inorganic and organic ARC materials is highlydesired.

This invention pertains to silsesquioxane resins that exhibitantireflective coating properties for 193 nm light. These antireflectivecoatings can be stripped at the removal stage and the silsesquioxaneresins are stable upon storage. In addition, the presence of a hydridegroup in the silsesquioxane resin is essential for the desired cureproperties and strip-ability as a 193 nm ARC material.

In particular this invention pertains to a method of forming anantireflective coating on an electronic device comprising

(A) applying to an electronic device an ARC composition comprising

(i) a silsesquioxane resin having the formula

(PhSiO_((3-x)/2)(OH)_(x))_(m)HSiO_((3-x)/2)(OH)_(x))_(n)(MeSiO_((3-x)/2)(OH)_(x))_(p)

where Ph is a phenyl group, Me is a methyl group, x has a value of 0, 1or 2; m has a value of 0.05 to 0.95, n has a value of 0.05 to 0.95, phas a value of 0.05 to 0.95, and m+n

+p≈1; and

(ii) a solvent; and

(B) removing the solvent and curing the silsesquioxane resin to form anantireflective coating on the electronic device.

The silsesquioxane resins (i) useful in forming the antireflectivecoating have the formula

(PhSiO_((3-x)/2)(OH)_(x))_(m)HSiO_((3-x)/2)(OH)_(x))_(n)(MeSiO_((3-x)/2)(OH)_(x))_(p)

where Ph is a phenyl group, Me is a methyl group, x has a value of 0, 1or 2; m has a value of 0.05 to 0.95, n has a value of 0.05 to 0.95, phas a value of 0.05 to 0.95, and m+n+p 1. Alternatively m has a value of0.05 to 0.50, n has a value of 0.10 to 0.70 and p has a value of 0.10 to0.70.

The silsesquioxane resin may be essentially fully condensed or may beonly partially condensed. When the silsesquioxane resin is partiallycondensed less than 40 mole % of the units in the silsesquioxane resinshould contain Si—OH groups. Higher amounts of these units can result ininstability in the resin and the formation of gels. Typically 6 to 38mole % of the units in the silsesquioxane resin contain Si—OH groups.

The silsesquioxane resin has a weight average molecular weight (Mw) inthe range of 500 to 400,000 and preferably in the range of 500 to100,000, alternatively 700 to 10,000.

Silsesquioxane resins useful herein may be exemplified by, but notlimited to

(PhSiO_(3/2))_(0.05-0.50)HSiO_(3/2))_(0.10-0.70)(MeSiO_(3/2))_(0.10-0.70)

(PhSiO_(3/2))_(a)(HSiO_(3/2))_(b)(MeSiO_(3/2))_(c)(RSiO_(2/2)(OH))_(d)(RSiO(OH)₂)_(e)

where R is selected form Ph, H and Me and 0.05≦a+d+e≦0.50,0.10≦b+d+e≦0.70, 0.10≦c+d+e≦0.70, 0.06≦d+e≦0.4, and a+b+c+d+e≈1.

The silsesquioxane resins may be produced by methods known in the art.For example, the silsesquioxane resins may be produced by the hydrolysisand condensation of a mixture of a phenyl trialkoxysilane, hydrogentrialkoxysilane and methyl trialkoxysilane. Alternatively they may beproduced by the hydrolysis and condensation of a phenyl trichlorosilane,hydrogen trichlorosilane and methyl trichlorosilane.

The silsesquioxane resin is typically produced in the presence of asolvent. Any suitable organic or silicone solvent that does not containa functional group which may participate in the reaction may be used inproducing the silsesquioxane resin. The solvent is generally used in anamount of 40 to 98 weight percent based on the total weight of solventand silane reactants, alternatively 70 to 90 weight percent. Thereaction may be carried out as a dual phase or single-phase system.

Useful organic solvents may be exemplified by, but not limited to,saturated aliphatics such as n-pentane, hexane, n-heptane, andisooctane; cycloaliphatics such as cyclopentane and cyclohexane;aromatics such as benzene, toluene, xylene, mesitylene; ethers such astetrahydrofuran, dioxane, ethylene glycol dietheyl ether, ethyleneglycol dimethyl ether; ketones such as methylisobutyl ketone (MIBK) andcyclohexanone; halogen substituted alkanes such as trichloroethane;halogenated aromatics such as bromobenzene and chlorobenzene; esterssuch as isobutyl isobutyrate and propyl propronate. Useful siliconesolvents may be exemplified by, but not limited to cyclic siloxanes suchas octamethylcyclotetrasiloxane, and decamethylcyclopentasiloxane. Asingle solvent may be used or a mixture of solvents may be used.

The reaction to produce the silsesquioxane resin can be carried out atany temperature so long as it does not cause significant gellation orcause curing of the silsesquioxane resin. Typically the reaction iscarried out at a temperature in the range of 5° C. to 150° C., withambient temperature suggested.

The time to form the silsesquioxane resin is dependent upon a number offactors such as the temperature, the type and amount of silanereactants, and the amount of catalyst, if present. Typically thereaction time is from several minutes to several hours. One skilled inthe art will be able to readily determine the time necessary to completethe reaction.

Following completion of the reaction the catalyst may be optionallyremoved. Methods for removing the catalyst are well know in the art andwould include neutralization, stripping or water washing or combinationsthereof. The catalyst may negatively impact the shelf life of thesilicone resin especially when in solution thus its removal issuggested.

In the process for making the silsesquioxane resin, after the reactionis complete, volatiles may be removed from the silsesquioxane resinsolution under reduced pressure. Such volatiles include alcoholby-products, excess water, catalyst, hydrochloric acid (chlorosilaneroutes) and solvents. Methods for removing volatiles are known in theart and include, for example, distillation.

Following the reaction to produce the silsesquioxane resin a number ofoptional steps may be carried out to obtain the silsesquioxane resin inthe desired form. For example, the silsesquioxane resin may be recoveredin solid form by removing the solvent. The method of solvent removal isnot critical and numerous methods are well known in the art (e.g.distillation under heat and/or vacuum). Once the silsesquioxane resin isrecovered in a solid form, the resin can be optionally re-dissolved inthe same or another solvent for a particular use. Alternatively, if adifferent solvent, other than the solvent used in the reaction, isdesired for the final product, a solvent exchange may be done by addinga secondary solvent and removing the first solvent through distillation,for example. Additionally, the resin concentration in solvent can beadjusted by removing some of the solvent or adding additional amounts ofsolvent.

An ARC composition is produced by combining the silsesquioxane resin (i)with a solvent (ii). The ARC composition is then applied to anelectronic device , the solvent is removed and the silsesquioxane resinis cured to produce the antireflective coating.

Typically the electronic device is a semiconductor device, such assilicon-based devices and gallium arsenide-based devices intended foruse in the manufacture of a semiconductor component. Typically, thedevice comprises at least one semiconductive layer and a plurality ofother layers comprising various conductive, semiconductive, orinsulating materials.

The solvent useful herein may be the same or different from the solventused in the production of the silsesquioxane resin. Useful solvents (ii)include, but are not limited to, 1-methoxy-2-propanol, propylene glycolmonomethyl ethyl acetate (PGMEA) and cyclohexanone, among others. TheARC composition typically comprises from about 10% to about 99.9 wt %solvent based on the total weight of the ARC composition, alternatively80 to 95 wt %.

The ARC composition can further comprise a cure catalyst. Suitable curecatalysts include inorganic acids, photo acid generators and thermalacid generators. Cure catalysts may be exemplified by, but not limitedto sulfuric acid (H₂SO₄), (4-ethylthiophenyl)methyl phenyl sulfoniumtriflate and 2-Naphthyl diphenylsulfonium triflate. Typically a curecatalyst is present in an amount of up to 1000 ppm, alternatively 500ppm, based on the total weight of the ARC composition.

Specific methods for application of the ARC composition to theelectronic device include, but are not limited to, spin-coating,dip-coating, spay-coating, flow-coating, screen-printing and others. Thepreferred method for application is spin coating. Typically, coatinginvolves spinning the electronic device, at about 2000 RPM, and addingthe ARC composition to the surface of the spinning electronic device.

The solvent is removed and the silsesquioxane resin is cured to form theanti-reflective coating on the electronic device. The solvent may beremoved by known methods such as heating or during application byspinning.

Curing generally comprises heating the coated electronic device to asufficient temperature for a sufficient duration to lead to curing. Forexample, the coated electronic device can be heated at 80° C. to 450° C.for 0.1 to 60 minutes, alternatively 150° C. to 275° C. for of 0.5 to 5minutes, alternatively 200° C. to 250° C. for 0.5 to 2 minutes. Anymethod of heating may be used during the curing step. For example, thecoated electronic device may be placed in a quartz tube furnace,convection oven or allowed to stand on hot plates.

To protect the silsesquioxane resin from reactions with oxygen or carbonduring curing, the curing step can be performed under an inertatmosphere. Inert atmospheres useful herein include, but are not limitedto nitrogen and argon. By “inert” it is meant that the environmentcontain less than 50 ppm and preferably less than 10 ppm of oxygen. Thepressure at which the curing and removal steps are carried out is notcritical. The curing step 1.5 is typically carried out at atmosphericpressure although sub or super atmospheric pressures may work also.

Once cured, the electronic device comprising the anti-reflective coatingcan be used in further substrate processing steps, such asphotolithography. When used in photolithography, a resist image isformed over the anti-reflective coating. The process for forming theresist image comprises (a) forming a film of a resist composition on topof the anti-reflective coating; (b) imagewise exposing the resist filmto radiation to produce an exposed film; and (c) developing the exposedfilm to produce an image. The anti-reflective coatings on the electronicdevice are particularly useful with resist compositions that areimagewise exposed to ultraviolet radiation having a wavelength of 157 nmto 365 nm, alternatively ultraviolet radiation having a wavelength of157 nm or 193 nm. Once an image has been produced in the resist film,then a pattern is etched in the anti-reflective coating. Known etchingmaterials may be used to remove the anti-reflective coating. Additionalsteps or removing the resist film and remaining anti-reflective coatingmay be employed to produce a device having the desired architecture.

The following examples are included to demonstrate preferred embodimentsof the invention. It should be appreciated by those of skill in the artthat the techniques disclosed in the examples which follow representtechniques discovered by the inventor to function well in the practiceof the invention, and thus can be considered to constitute preferredmodes for its practice. However, those of skill in the art should, inlight of the present disclosure, appreciate that many changes can bemade in the specific embodiments which are disclosed and still obtain alike or similar result without departing from the spirit and scope ofthe invention.

EXAMPLES Resin Synthesis Example 1 T^(Ph) _(0.25)T^(H) _(0.30)T^(Me)_(0.45)

A solution of 120 grams of PGMEA, 13.2 grams (0.0625 moles) ofphenyltrichlorosilane, 10.16 grams (0.075 moles) of trichlorosilane,16.82 g (0.1125 moles) of methyltrichlorosilane were transferred to thereactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=1876 Å, n=1.797, k=0.5625.

Example 2 T^(Ph) _(0.55)T^(H) _(0.35)T^(Me) _(0.10)

A solution of 120 grams of PGMEA, 29.09 grams (0.1375 moles) ofphenyltrichlorosilane, 11.85 grams (0.0875 moles) of trichlorosilane,3.74 g (0.025 moles) of methyltrichlorosilane were added to a reactorunder nitrogen. A solution of 200 grams of PGMEA and 10 grams (0.555moles) of water was added to the solution of trichlorosilanes over aone-hour period. The reaction was allowed to body, stirring at 20° C.for one hour. The resin solution was then washed with 100 mL DI waterand the water was discarded. Approximately 40 grams of ethanol was addedto the resin solution. The solution was stripped to approximately 20 wt% of solid and then diluted to 10 wt % with PGMEA. The solution wasfiltered through a 0.20 micron PTFE filter and stored in a 250 mL HDPEbottle. Thickness=2147 Å, n=1.887, k=0.769.

Example 3 T^(Ph) _(0.05)T^(H) _(0.35)T^(Me) _(0.60)

A solution of 120 grams of PGMEA, 2.64 grams (0.0125 moles) ofphenyltrichlorosilane, 11.85 grams (0.0875 moles) of trichlorosilane,22.42 g (0.15 moles) of methyltrichlorosilane were added to a reactorunder nitrogen. A solution of 200 grams of PGMEA and 10 grams (0.555moles) of water was added to the solution of trichlorosilanes over aone-hour period. The reaction was allowed to body, stirring at 20° C.for one hour. The resin solution was then washed with 100 mL DI waterand the water was discarded. Approximately 40 grams of ethanol was addedto the resin solution. The solution was stripped to approximately 20 wt% of solid and then diluted to 10 wt % with PGMEA. The solution wasfiltered through a 0.20 micron PTFE filter and stored in a 250 mL HDPEbottle. Thickness=2318 Å, n=1.612, k=0.093.

Example 4 T^(Ph) _(0.10)T^(H) _(0.10)T^(Me) _(0.60)

A solution of 120 grams of PGMEA, 5.29 grams (0.025 moles) ofphenyltrichlorosilane, 10.16 grams (0.075 moles) of trichlorosilane,22.42 g (0.15 moles) of methyltrichlorosilane were transferred to areactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=1992 Å, n=1.680, k=0.208.

Example 5 T^(Ph) _(0.10)T^(H) _(0.60)T^(Me) _(0.30)

A solution of 120 grams of PGMEA, 5.29 grams (0.025 moles) ofphenyltrichlorosilane, 20.32 grams (0.15 moles) of trichlorosilane,11.21 g (0.075 moles) of methyltrichlorosilane were transferred to areactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=1322 Å, n=1.630, k=0.198.

Example 6 T^(Ph) _(0.10)T^(H) _(0.70)T^(Me) _(0.20)

A solution of 120 grams of PGMEA, 5.29 grams (0.025 moles) ofphenyltrichlorosilane, 23.70 grams (0.175 moles) of trichlorosilane,7.47 g (0.05 moles) of methyltrichlorosilane were transferred to areactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=2938 Å, n=1.610, k=0.202.

Example 7 T^(Ph) _(0.10)T^(H) _(0.35)T^(Me) _(0.55)

A solution of 120 grams of PGMEA, 5.29 grams (0.025 moles) ofphenyltrichlorosilane, 11.85 grains (0.088 moles) of trichlorosilane,20.55 g (0.138 moles) of methyltrichlorosilane were transferred to areactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=2008 Å, n=1.610, k=0.202.

Example 8 T^(Ph) _(0.10)T^(H) _(0.45)T^(Me) _(0.45)

A solution of 120 grams of PGMEA, 5.29 grams (0.025 moles) ofphenyltrichlorosilane, 15.24 grams (0.1125 moles) of trichlorosilane,16.82 g (0.1125 moles) of methyltrichlorosilane were transferred to areactor under nitrogen. A solution of 200 grams of PGMEA and 10 grams(0.555 moles) of water was added to the solution of trichlorosilanesover a one-hour period. The reaction was allowed to body, stirring at20° C. for one hour. The resin solution was then washed with 100 mL DIwater and the water was discarded. Approximately 40 grams of ethanol wasadded to the resin solution. The solution was stripped to approximately20 wt % of solid and then diluted to 10 wt % with PGMEA. The solutionwas filtered through a 0.20 micron PTFE filter and stored in a 250 mLHDPE bottle. Thickness=1430 Å, n=1.630, k=0.198.

Application Examples Film Coating and Characterization

The film coating on wafers was processed on a Karl Suss CT62 spincoater. Solutions of resin in PGMEA were first filtered through a 0.2micron PTFE filter and then spin coated onto standard single side fourinch polished low resistivity wafers or double sided polished FTIRwafers (spin speed=2000 rpm; acceleration speed=5000, time=20 seconds).Films were cured at a temperature (200-250° C.) for 90 seconds asindicated in the tables using a rapid thermal processing (RTP) oven witha nitrogen gas purge. The film thickness, refractive index and k valuewere determined using a J. A. Woollam ellipsometer. The thickness valuesrecorded were the average of nine measurements. PGMEA resistance of thefilm after cure was determined by measuring the film thickness changebefore and after PGMEA hold (one minute) and rinse (ΔTh¹ Å);tetramethylammonium hydroxide (TMAH) resistance after cure wasdetermined by measuring the film thickness change before and after TMAHhold (one minute) and rinse (ΔTh² Å). Contact angle measurements usingwater and methylene iodide as liquids were used to calculate thecritical surface tension of wetting using the Zisman approach. All ofthe cured films made from the above resins were completely stripped withtwo commercial wet stripping solution NE89 and CC1.

TABLE 1 shows the results PGMEA resistance and TMAH resistance for 4different resins (App 1-4). Example App4 corresponds to the resin fromExample 1.

TABLE 2 shows that the process for making the resin is reproducible.Example App 5 is a scale up of the resin made in Example App 4. As canbe seen the MW and the performance are very close. Example App 5 afterbake at 225° C. for 60 seconds had a water contact angle of 84.3 and asurface energy of 32.6. Example App 5 after bake at 250° C. for 60seconds had a water contact angle of 86 and a surface energy of 32.6.

TABLE 3 shows the resin of Example 4 used as a hard mask.

TABLE 1 Application Examples 1-4. Bake Temp Th ΔTh¹ ΔTh² Example Resin °C. (Å) (Å) (Å) App1 T^(Ph) _(0.10)T^(H) _(0.25)T^(Me) _(0.65) 250 1916 01916 10 App2 T^(Ph) _(0.10)T^(H) _(0.30)T^(Me) _(0.60) 250 1992 1 201725 App3 T^(Ph) _(0.25)T^(H) _(0.20)T^(Me) _(0.55) 225 1037 239 1038 13250 1012 77 1023 5 App4 T^(Ph) _(0.25)T^(H) _(0.30)T^(Me) _(0.45) 2251876 27 1851 29 250 1861 4 1860 5

TABLE 2 Application Examples 4 and 5 M_(w) vs. M_(w)/M_(n) Bake T ThΔTh¹ ΔTh² Example PS vs PS ° C. (Å) (Å) (Å) App 4-1 5560 3.3 225 1876 27App 4-2 225 1851 29 App 4-3 250 1861 4 App 4-4 250 1860 5 App 5-1 57103.2 225 2003 240 App 5-2 225 2000 21 App 5-3 250 1961 18 App 5-4 2501974 25

TABLE 3 Application of resin Example 6. Bake T Th ΔTh¹ ΔTh² Watercontact Surface Energy Example ° C. Å Å Å Angle (°) App 6-1 250 1992 193 29.9 App 6-1 250 2017 25

1-16. (canceled)
 17. An antireflecting coating (ARC) composition comprising (i) a silsesquioxane resin having the formula (PhSiO_((3-x)/2)(OH)_(x))_(m)(HSiO_((3-x)/2)(OH)_(x))_(n)(MeSiO_((3-x)/2)(OH)_(x))_(p) where Ph is a phenyl group, Me is a methyl group, x has a value of 0, 1 or 2; m has a value of 0.05 to 0.95, n has a value of 0.05 to 0.95, p has a value of 0.05 to 0.95, and m+n+p≈1; (ii) a solvent.
 18. The composition as claimed in claim 17 wherein m has a value of 0.05 to 0.50, n has a value of 0.10 to 0.70 and p has a value of 0.10 to 0.70.
 19. The composition as claimed in claim 17 wherein in the silsesquioxane resin less than 40 mole % of the units contains Si—OH groups.
 20. The composition as claimed in claim 17 wherein in the silsesquioxane resin 6 to 38 mol % of the units contain Si—OH groups.
 21. The composition as claimed in claim 17 wherein the solvent (ii) is selected from 1-methoxy-2-propanol, propylene methyl ether acetate and cyclohexanone.
 22. The composition as claimed in claim 17 wherein the composition contains 80 to 95 wt % of solvent, based on the weight of the composition.
 23. The composition as claimed in claim 17 wherein the composition additionally contains a cure catalyst. 